CN112480493B - Rubber foaming material and preparation method thereof - Google Patents

Abstract

The invention discloses a rubber foaming material and a preparation method thereof. The foaming material is prepared from the following raw materials: 100 parts by weight of rubber latex; 5-200 parts by weight of curdlan; 10-500 parts by weight of a heat-conducting filler; 0.5-20 parts by weight of a surfactant; 1-5 parts of a vulcanizing agent. The preparation method comprises the following steps: adding the heat-conducting filler, the surfactant and the curdlan into deionized water, stirring and mixing uniformly, then adding other components, stirring at a low speed until the mixture is uniformly mixed, and then stirring at a high speed to start foaming; continuously stirring and foaming, and carrying out heat treatment on the foaming liquid; then cooling to room temperature to obtain hydrogel, drying the hydrogel and vulcanizing. The invention improves the traditional latex foaming process, introduces gel polysaccharide as a gelling agent, and realizes the preparation of high-filler-filling, low-density and super-elastic rubber foam.

Description

Rubber foaming material and preparation method thereof

Technical Field

The invention relates to the technical field of rubber, in particular to a rubber foam material which is light, super-elastic, high-flexibility, controllable in heat conduction.

Background

Thanks to the rapid development of science and technology, the appearance of electronic products is continuously miniaturized, so as to facilitate the daily use of people. Meanwhile, the functions of electronic products are more and more powerful, and the performance is exponentially improved. But the working power per unit volume in the electronic product is greatly increased while more functions and higher efficiency are given to the electronic product. It has been reported that current high power electronic devices dissipate power densities of up to 1000W/cm during operation^-2Thereby causing a serious heat dissipation problem. On the one hand, joule heat is generated by the current passing through any conductor, and part of the power loss is converted into heat, so that the electronic device in operation is a small heat source. On the other hand, high performance of electronic products is based on high power consumption, and batteries also generate heat when they are discharged quickly. If the heat cannot be effectively dissipated, the internal temperature of the electronic product will continuously rise until the performance of the electronic product with thermal failure is strong due to the burning of part of components, and the thermal failure will be more likely to occur because the heat flux will be larger and larger as the power density of the semiconductor device is continuously increased, and the heat dissipation will be more and more difficult. If the accumulated heat cannot be dissipated from the components in time, the stability of the electronic product can be seriously threatened, and researches show that more than half of faults in the electronic device are caused by the problems related to the heat. It is generally accepted by the industry whether effective heat dissipation materials can be prepared, rather than the hardware itself and heat dissipation design, as a bottleneck in future electronic product development. The structural design of the composite material is carried out, the heat-conducting property of the composite material is improved, the problem of increasingly serious thermal failure in modern electronic products is solved, and the composite material is a key research direction in the international electronic and electrical research field at present.

Nowadays, with the increasing demand of modern electronic products for heat dissipation, the demand of novel heat-conducting composite materials is great. Compared to other thermally conductive materials, such as metals, ceramics and carbon-based materials, polymer-based composites have the following advantages: 1. the processing is easy, and the complex geometric shape can be processed; 2. the weight is light; 3. chemical corrosion resistance; 4. the flexible polymer can be in close contact with the rough surface of the object; 5. and (5) vibration reduction. The rubber material is a material with intrinsic high flexibility and high elasticity, and is an excellent substrate used as a thermal interface material. At present, thermal interface materials using liquid silicone rubber as a matrix have been widely used. However, various general-purpose rubbers, such as natural rubber, styrene butadiene rubber, etc., are limited by processing methods and have low thermal conductivity, and no suitable high thermal conductivity product is available.

In addition, lithium ion batteries do not perform well at extreme temperatures, preventing their widespread use in the energy field. One of the basic challenges of battery thermal management systems is that the cold-hot environment is the opposite of the battery requirements, namely heat transport at high temperatures to achieve cooling of the battery and thermal isolation at low temperatures to maintain the heat generated inside the battery, inevitably resulting in a compromise in hot or cold performance.

The development of a material capable of preserving heat at low temperature and dissipating heat at high temperature is a technical problem to be solved urgently at present.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a rubber foaming material and a preparation method thereof. The invention improves the traditional latex foaming process, introduces gel polysaccharide as a gelling agent, and realizes the preparation of high-filler-filling, low-density and super-elastic rubber foam.

The rubber foaming material has the advantages of softness, good elasticity and the like, and is generally applied to the latex pillow industry at present. The rubber foam material has a large number of hollow structures inside, so that the rubber foam material has extremely low thermal conductivity in an uncompressed state and is in a heat insulation state. The traditional foaming material has low thermal conductivity even after internal pores are removed by compression, which is caused by low thermal conductivity of pure rubber materials. In order to ensure that the rubber foaming material has higher thermal conductivity after the cavities are removed by compression, the heat-conducting filler is added when the rubber foaming material is foamed. Therefore, the rubber foaming material is in a heat insulation state before compression, and the heat conductivity is greatly improved after air holes are removed by compression, so that the rubber foaming material has double effects of heat preservation and heat dissipation.

One of the purposes of the invention is to provide a rubber foaming material.

The foaming material is prepared from the following raw materials:

the components are calculated according to the parts by weight,

the heat-conducting filler in the invention can be selected from all heat-conducting fillers in the prior art, and is preferably one or a combination of hexagonal boron nitride, cubic boron nitride, graphene nanosheets, graphite, carbon fibers, carbon nanotubes, aluminum oxide, zinc oxide, metallic silver, metallic copper, silicon carbide, beryllium oxide, aluminum nitride, carbon nitride, diamond, magnesium oxide, MXene, carbon black and white carbon black.

The surfactant in the invention can be selected from surfactants conventional in the prior art, and is preferably one or a combination of sodium dodecyl benzene sulfonate, various alkyl glycosides, dodecyl ammonium bromide, potassium oleate soap, alkylphenol polyoxyethylene ether (OP, NP, TX) series emulsifiers, fatty alcohol polyoxyethylene ether (AEO) series emulsifiers, (peregal) series emulsifiers, sorbitan fatty acid ester polyoxyethylene ether (Tween series) emulsifiers, sorbitan fatty acid ester (span series) emulsifiers, coconut oil diethanolamide (6501) emulsifiers, potassium oleate soap and the like.

The rubber latex in the invention can be selected from all rubber latexes in the prior art, and is preferably one or a combination of natural latex, styrene-butadiene latex, butyronitrile latex, chloroprene latex, cis-butadiene latex, epoxidized natural rubber latex, butadiene-pyrene latex, carboxyl butyronitrile latex, acrylic latex, silica gel latex, polyurethane latex and the like.

The vulcanizing agent in the invention can be selected from vulcanizing agents conventional in the prior art, and preferably, the vulcanizing agent is one or more of sulfur, dicumyl peroxide and 2, 5-dimethyl-2, 5-di (tert-butylperoxy) hexane.

The formulations of the invention may also comprise conventional auxiliaries, such as: the dosage of the activating agent, the accelerator, the anti-aging agent and the like is also conventional, and the technical personnel can adjust the dosage according to the actual situation.

The activating agent in the invention can be selected from activating agents conventional in the prior art, and preferably, the activating agent is one or more of common rubber activating agents such as zinc oxide, magnesium oxide, zinc carbonate, zinc hydroxide, organic zinc, stearic acid and the like.

The accelerator used in the present invention may be any conventional accelerator in the prior art, and preferably one or more of conventional rubber accelerators such as accelerator DM (benzothiazole disulfide), accelerator CZ (N-cyclohexyl-2-benzothiazole sulfenamide), accelerator NS (N-tert-butyl-2-benzothiazole sulfenamide), accelerator TMTD (tetramethylthiuram disulfide), accelerator TMTM (tetramethylthiuram monosulfide), accelerator DTDM (4, 4 '-dithiodimorpholine), accelerator D (1, 3-diphenylguanidine), accelerator NOBS (N- (oxydiethylene) -2-benzothiazole sulfenamide) and accelerator DM (2, 2' -dithiodibenzothiazole) are used.

The antioxidant in the invention can be selected from the conventional antioxidants in the prior art, and preferably one or more of common rubber accelerators such as antioxidant 4010NA (N-isopropyl-N '-phenyl-p-phenylenediamine), antioxidant RD (2,2, 4-trimethyl-1, 2-dihydroquinoline polymer), antioxidant 4020(N- (1, 3-dimethyl) butyl-N' -phenyl-p-phenylenediamine), antioxidant AW (6-ethoxy-2, 2, 4-trimethyl-1, 2-dihydroquinoline), antioxidant D (N-phenyl-beta-naphthylamine), antioxidant TPPD (N-N-phenyl-p-phenylenediamine) and the like.

The preferred amounts in the present invention are (based on 100 parts by weight of the rubber latex):

1-10 parts by weight of an activating agent; more preferably 2 to 4 parts by weight;

1-5 parts by weight of an accelerator; more preferably 0.5 to 3 parts by weight;

1-10 parts of an anti-aging agent; more preferably 2 to 4 parts by weight.

The second purpose of the invention is to provide a preparation method of the rubber foaming material.

The method comprises the following steps:

adding the heat-conducting filler, the surfactant and the curdlan into deionized water, stirring and mixing uniformly, preferably, the concentration is 3-30 wt%, then adding other components, stirring at a low speed until the mixture is uniformly mixed, and then stirring at a high speed to start foaming; continuously stirring and foaming, and carrying out heat treatment on the foaming liquid; and then cooling to room temperature to obtain hydrogel, drying the hydrogel and vulcanizing to obtain the rubber foaming material.

Among them, preferred are:

the rotating speed of the low-speed stirring is less than 600 revolutions per minute;

the high-speed stirring speed is more than 800 rpm.

The heat treatment temperature of the foaming liquid is 70-90 ℃, and the heat treatment time is 2-20 min.

The addition form of other components in the preparation method is not limited, and the other components can be directly added or added in the form of dispersion liquid; more preferably, the vulcanizing agent is added in the form of a dispersion.

Adding the heat-conducting filler, the surfactant and the curdlan into deionized water, stirring and mixing uniformly, preferably: the surfactant concentrations were: 0.5 wt% -2 wt%; the gel polysaccharide concentration was: 0.5 wt% -5 wt%; the concentration of the heat-conducting filler is as follows: 2.5 wt% -20 wt%.

The basic principle of the invention is to prepare the functional rubber foaming material filled with high filler amount by combining a surfactant latex foaming method and gel polysaccharide gelation. Curdlan is a polysaccharide substance extracted from nature, also called curdlan, and is now commonly used in food industry for food gelatinization. The gel polysaccharide has unique property that irreversible gelation can occur at high temperature, and the invention firstly utilizes the property to gel the rubber latex foamed by the surfactant and the foaming liquid of the heat-conducting filler at high temperature, and then directly places the gelled latex and the foaming liquid of the heat-conducting filler in an oven to be vulcanized and dried. The gelation of curdlan successfully constructs a framework of the heat-conducting filler, and the framework has good resilience and toughness due to the existence of latex particles.

The invention adopts the following specific technical scheme:

the heat-conducting filler, the surfactant and the curdlan are put into a certain amount of deionized water to be stirred and mixed uniformly, and then the rubber latex, the vulcanizing agent, the activator, the accelerator, the antioxidant and the like are added to be stirred uniformly. Mixing at low speed (less than 600 rpm) until uniform, and then raising the rotation speed to start foaming. And (3) placing the foaming solution in an environment of 70-90 ℃ for heat treatment, and then continuously stirring for foaming. And then pouring the heat-treated foaming liquid into a mold. When the foaming liquid is cooled to room temperature, the foaming liquid is gelled to form hydrogel. And (3) placing the hydrogel in a drying oven for drying and vulcanizing. The drying process and the vulcanizing process can be carried out in sequence, namely, drying first and then vulcanizing, or vulcanizing first and then drying, or simultaneously. 1. Firstly vulcanizing and then drying: firstly, sealing hydrogel, vulcanizing at high temperature, rinsing, and drying to obtain a foam material 2, vulcanizing and drying simultaneously: firstly, exposing hydrogel in an oven, drying and vulcanizing at high temperature, then rinsing and drying to obtain a foam material 3, firstly drying and then vulcanizing: firstly, the hydrogel is exposed in an oven and dried at low temperature, then the hydrogel is vulcanized at higher vulcanization temperature after being dried (corresponding compression treatment can be carried out), and finally the hydrogel is rinsed and dried to obtain the foam material.

The small materials such as the vulcanizing agent, the activating agent, the accelerator, the anti-aging agent and the like related by the invention are not limited by the adding method, can be directly added, and can also be prepared into a stable aqueous dispersion liquid commonly used in the latex product industry in advance for adding; the addition amount of the small materials is reasonably determined according to the parts of the added rubber, and normal vulcanization can be ensured.

The stirring in the invention is not limited to equipment, and for example, a special foaming machine can be used for stirring, and a common stirring paddle can be used for stirring. The stirring speed during foaming is determined according to actual conditions, stable foaming can be ensured, and the foaming multiplying power is generally 1.5-5 times for foaming.

The drying process and the vulcanizing process of the foaming liquid hydrogel obtained in the invention can be carried out in sequence of drying first and then vulcanizing, or in sequence of vulcanizing first and then drying, or simultaneously.

1. Firstly vulcanizing and then drying: firstly, sealing the hydrogel, vulcanizing at 80-110 ℃, rinsing, and drying to obtain the foaming material

2. The vulcanization and drying are carried out simultaneously: firstly, the hydrogel is exposed in an oven, dried and vulcanized at the temperature of 80-110 ℃, and then rinsed and dried to obtain the foaming material

3. Drying and then vulcanizing: firstly, exposing the hydrogel in an oven for drying at the temperature of below 60 ℃, then placing the hydrogel at the vulcanization temperature of 90-170 ℃ for vulcanization after the drying is finished, and finally rinsing and drying the hydrogel to obtain the foaming material.

The vulcanization time of the invention is determined according to the dosage of different rubbers, different vulcanizing agents and accelerators.

The invention has the advantages of

1. According to the invention, the curdlan is introduced into latex foaming to serve as a high-temperature gel agent, the traditional hazardous chemical gelling agent is replaced, the process conditions are mild, simple and environment-friendly, the applicable system is wide, and the industrial value is very high.

2. The invention successfully constructs a filler three-dimensional network by combining gel polysaccharide gelation with a surfactant foaming method, and introduces latex to increase the elasticity and toughness of the filler.

3. The three-dimensional foam framework obtained by the invention has extremely high designability, and can be endowed with heat conduction and other functionalities according to different selected fillers.

Drawings

FIG. 1 is a schematic view of the scanning electron microscope for microscopic analysis of the composite material prepared in example 1.

Detailed Description

While the present invention will be described in detail and with reference to the specific embodiments thereof, it should be understood that the following detailed description is only for illustrative purposes and is not intended to limit the scope of the present invention, as those skilled in the art will appreciate numerous insubstantial modifications and variations therefrom.

The gel polysaccharide used in the invention is a product of Shanghai-sourced leaf biotechnology limited company with the product number of S11046; other raw materials are all common commercially available medicines.

Comparative example 1

The formula is as follows:

the components are calculated according to the parts by weight,

the specific implementation process is as follows:

100 g of natural rubber latex (60% by weight), 2 g of potassium oleate soap dispersion (50% by weight), 3 g of sulfur dispersion (50% by weight), 2 g of accelerator ZDEC dispersion (50% by weight), 2 g of accelerator MZ dispersion (50% by weight), 1 g of accelerator D dispersion (50% by weight), 4 g of anti-aging agent 4020 dispersion (50% by weight) and the like were stirred uniformly. And (3) curing, foaming for 5min, mixing with 4 g of zinc oxide dispersion (50 wt%) and 1 g of sodium fluosilicate, continuing foaming, pouring into a mold for gelation, vulcanizing at 100 ℃ for 2 hours, and finally rinsing and drying to obtain the latex foam material.

Example 1

The formula is as follows:

the components are calculated according to the parts by weight,

the specific implementation process is as follows:

10 g of hexagonal boron nitride, 1 g of alkyl glycoside and 2 g of curdlan are put into 100 g of deionized water and stirred and mixed uniformly, and then 16.7 g of natural rubber latex (60% wt), 0.3 g of sulfur dispersion (50% wt), 0.4 g of zinc oxide dispersion (50% wt), 0.2 g of accelerator ZDEC dispersion (50% wt), 0.2 g of accelerator MZ dispersion (50% wt), 0.1 g of accelerator D dispersion (50% wt), 0.4 g of antioxidant 4020 dispersion (50% wt) and the like are added and stirred uniformly. Stirring at 600 rpm for 5min, mixing, and raising the rotation speed to 1500 rpm to start foaming. And (3) placing the foaming solution in an environment of 80 ℃ for heat treatment for 10min, and then continuously stirring and foaming. And then pouring the heat-treated foaming liquid into a mold. When the foaming liquid is cooled to room temperature, the foaming liquid is gelled to form hydrogel. And taking out the obtained hydrogel, and putting the hydrogel into an oven at 80 ℃ for drying and vulcanizing for 6 hours at the same time to obtain the foam material. Finally rinsing and drying by using a large amount of clear water to obtain a final product.

Example 2

The formula is as follows:

the components are calculated according to the parts by weight,

the specific implementation process is as follows:

2.5 g of carbon nano tube, 1 g of triton X-100 emulsifier and 5 g of curdlan are put into 100 g of deionized water and stirred and mixed uniformly, and then 8.3 g of styrene butadiene rubber latex (60% wt), 0.15 g of sulfur dispersion (50% wt), 0.2 g of zinc oxide dispersion (50% wt), 0.1 g of accelerator ZDEC dispersion (50% wt), 0.1 g of accelerator MZ dispersion (50% wt), 0.05 g of accelerator NS dispersion (50% wt), 0.2 g of antioxidant 4020 dispersion (50% wt) and the like are added and stirred uniformly. Stirring at 600 rpm for 5min, mixing, and raising the rotation speed to 2000 rpm to start foaming. And (3) placing the foaming solution in an environment of 70 ℃ for heat treatment for 20min, and then continuously stirring and foaming. And then pouring the heat-treated foaming liquid into a mold. When the foaming liquid is cooled to room temperature, the foaming liquid is gelled to form hydrogel. And sealing the obtained hydrogel, putting the hydrogel into an oven at 100 ℃ for vulcanization for 2 hours, rinsing the vulcanized hydrogel, and drying to obtain the foam material.

Example 3

The formula is as follows:

the components are calculated according to the parts by weight,

the specific implementation process is as follows:

20 g of alumina, 0.5 g of Tween 20 emulsifier and 0.5 g of curdlan are put into 100 g of deionized water and stirred and mixed uniformly, and then 8.3 g of epoxidized natural rubber latex (60% wt), 0.15 g of sulfur dispersion (50% wt), 0.2 g of zinc oxide dispersion (50% wt), 0.1 g of accelerator NS dispersion (50% wt), 0.15 g of accelerator TMTD dispersion (50% wt), 0.2 g of antioxidant RD dispersion (50% wt) and the like are added and stirred uniformly. Stirring at 2500 rpm for 5min, mixing, and raising the rotation speed to 1500 rpm to start foaming. And (3) placing the foaming solution in an environment of 90 ℃ for heat treatment for 2min, and then continuously stirring and foaming. And then pouring the heat-treated foaming liquid into a mold. When the foaming liquid is cooled to room temperature, the foaming liquid is gelled to form hydrogel. And (3) drying the obtained hydrogel in a 50 ℃ oven for 5 hours, vulcanizing the dried gel at 150 ℃ for 30min to obtain a foaming material, and finally rinsing and drying the foaming material by using a large amount of clear water to obtain a final product.

Example 4

The formula is as follows:

the components are calculated according to the parts by weight,

the specific implementation process is as follows:

5 g of graphene nanosheet, 0.5 g of span-80 emulsifier and 5 g of curdlan are put into 100 g of deionized water and stirred and mixed uniformly, and then 8.3 g of chloroprene rubber latex (60% wt), 0.4 g of DCP dispersion liquid (20% wt), 0.4 g of anti-aging agent 4010NA dispersion liquid (50% wt) and the like are added and stirred uniformly. Stirring at 400 rpm, ultrasonically mixing for 10min, and raising the rotation speed to 1200 rpm to start foaming. And (3) placing the foaming solution in an environment of 85 ℃ for heat treatment for 5min, and then continuously stirring and foaming. And then pouring the heat-treated foaming liquid into a mold. When the foaming liquid is cooled to room temperature, the foaming liquid is gelled to form hydrogel. And (3) drying the obtained hydrogel in a 60 ℃ oven for 3 hours, then vulcanizing at 170 ℃ for 10min to obtain a foaming material, and finally rinsing and drying with a large amount of clear water to obtain a final product.

Description of the test results

From FIG. 1, it can be seen that the foamed material has a cell structure with a size of hundreds of microns distributed therein, and the boron nitride flake filler can be seen in the cell wall and has a rubber skeleton.

The resulting foams were compressed to 60% or more of the resulting volume, and the foams of comparative example and example were tested for thermal conductivity before and after compression (test standard GB/T1.1-2009), with the results shown in table 1.

TABLE 1

As can be seen from table 1, the thermal conductivity after compression of comparative example 1 is significantly lower than that of examples 1-4, apparently due to the construction of the filler skeleton in the examples. Before compression, the thermal conductivity of the porous material is in a high thermal insulation state, the thermal conductivity is greatly improved after compression, and the thermal conductivity property after thermal insulation compression before compression has extremely high application prospect in lithium battery thermal management.

While the invention has been described in detail with reference to the foregoing examples, it is not intended to be limited to the details shown, since various equivalent modifications, such as changes in the formulation of ingredients with different activators, curatives, etc., and in the order of addition/processing/article-forming processing, can be made by those skilled in the art. Such equivalent modifications and substitutions are intended to be included within the scope of the present application.

Claims (7)

1. The rubber foaming material is characterized by being prepared from the following raw materials:

the components are calculated according to the parts by weight,

the heat-conducting filler is one or a combination of hexagonal boron nitride, cubic boron nitride, graphene nanosheets, graphite, carbon fibers, carbon nanotubes, aluminum oxide, metallic silver, metallic copper, silicon carbide, beryllium oxide, aluminum nitride, carbon nitride, diamond, magnesium oxide, MXene, carbon black and white carbon black.

2. The rubber foam according to claim 1, wherein:

the surfactant is one or a combination of sodium dodecyl benzene sulfonate, alkyl glycoside, dodecyl ammonium bromide, potassium oleate soap, alkylphenol polyoxyethylene, fatty alcohol polyoxyethylene ether, sorbitan fatty acid ester polyoxyethylene ether, peregal series emulsifier, sorbitan fatty acid ester, coconut oil diethanolamide and potassium oleate soap.

3. The rubber foam according to claim 1, wherein:

the rubber latex is one or a combination of natural latex, styrene-butadiene latex, butyronitrile latex, neoprene latex, cis-butadiene latex, epoxidized natural rubber latex, butadiene-pyrene latex, carboxylated butyronitrile latex, acrylic latex, silica gel latex, polyurethane latex and the like.

4. A method for producing the rubber foam according to any one of claims 1 to 3, characterized by comprising:

adding the heat-conducting filler, the surfactant and the curdlan into deionized water, stirring and mixing uniformly, then adding other components, stirring at a low speed until the mixture is uniformly mixed, and then stirring at a high speed to start foaming; continuously stirring and foaming, and carrying out heat treatment on the foaming liquid; and then cooling to room temperature to obtain hydrogel, drying the hydrogel and vulcanizing to obtain the rubber foaming material.

5. The method of claim 4, wherein:

the rotating speed of the low-speed stirring is less than 600 revolutions per minute;

the high-speed stirring speed is more than 800 rpm.

6. The method of claim 4, wherein:

the heat treatment temperature of the foaming liquid is 70-90 ℃, and the heat treatment time is 2-20 min.

7. The method of claim 4, wherein:

adding the heat-conducting filler, the surfactant and the curdlan into deionized water, and uniformly stirring and mixing, wherein the concentration of the solution is 3-30 wt%.

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